Wideband Circularly Polarized Antenna With Dual-Mode Operation

This letter presents a simple structure of a singlefed broadband circularly polarized (CP) antenna. The antenna consists of four L-shaped strips that rotate in sequence and a double vacant-quarter ring. The double vacant-quarter ring primarily contributes to the wide axial-ratio bandwidth, while the L-shaped strip primarily contributes to the wide axial-ratio beamwidth, with the two modes combined to achieve a wideband CP operation. A prototype antenna was designed, fabricated, and measured. The measured results show that the proposed antenna yields a 10 dB impedance bandwidth of 92.8% (4.5-12.3 GHz), a 3 dB axial-ratio bandwidth of 67.5% (5.3-10.7 GHz), and a 3 dB gain bandwidth of 62.3% (5.3-10.1 GHz) with a peak gain of 12.4 dBic.